1. Field of the Invention
The invention relates to a screw-type extrusion machine comprising a composite casing which comprises casing sections fitted together in a longitudinal direction, the casing sections being tightly tautened relative to each other by a plurality of tie rods which extend parallel to each other in the longitudinal direction of the casing on the outside thereof.
2. Background Art
A screw-type extrusion machine of the generic type is known from DE39 36 085 A1.
DE 29 52 348 A1 describes a connection of casing sections, in particular for twin-screw extruders, the casing sections being connected with each other by means of pre-stressed threaded bolts which are disposed in two planes axially parallel to the double cylinder bores and diametrically opposed to each other. In order to obtain the pre-stress, the threaded bolts are heated so that when they cool down, the desired pre-stress is occasioned due to the reduction in length.
In other screw-type extrusion machines of the generic type known from prior public use, four tie rods parallel to each other are disposed in closed drill holes of the housing sections. During assembly, the housing sections are threaded on the tie rods. Provided the housing and tie rods are exposed to the same temperature during the heating-up phase and in the heated condition with no different thermal elongations occurring, a reliably tight arrangement of the housing sections relative to each other can be achieved. If, however, in the case of larger and heavier machines, regular temperature distribution is no longer ensured, problems of tightness may occur.